Sushi made with raw fish

Occasionally, raw fish like salmon contains small parasitic worms, such as anisakis, which can make you ill. These worms can cause health problems in people if they eat raw or undercooked fish infected with them.

Infection with these worms results in a condition known as anisakidosis (formerly known as anisakiasis or anisakiosis).

The disease is unpleasant and painful, and in very rare cases can be fatal. Eating fish contaminated with anisakis can also cause an allergic reaction. Freezing raw wild fish kills any worms that may be present and makes it safe to eat.

Certain farmed fish destined to be eaten raw in dishes like sushi, such as farmed salmon, no longer need to be frozen beforehand. This is because these particular types of farmed fish are very unlikely to contain parasitic worms because of the rearing methods used.

Sushi made with cured fish

Some fish used to make sushi, such as smoked salmon, doesn't need to be frozen before it's used because most smoking processes kill any parasitic worms in the fish. Other methods, such as salting or pickling, also make raw fish safe to eat.

Sushi made with shellfish

A lot of sushi contains shellfish, such as:

shrimps

prawns

crabs

scallops

When you're pregnant, you should only eat cooked shellfish. Raw shellfish can contain harmful viruses and bacteria that can cause food poisoning.

If you eat sushi prepared in a restaurant, ask if the shellfish in it has been cooked.

Sushi from shops and restaurants

Lots of the sushi sold in shops isn't made at the shop. This type of sushi should be fine to eat because if a shop or restaurant buys in ready-made sushi, the raw fish used to make it will have been subject to an appropriate freezing treatment.

Homemade sushi

If you make your own sushi at home, freeze the fish for at least 4 days before using it.